You can make money from calling 3bets and more importantly you lose less than the 3bb you opened to preflop in the long run.. that's also money won..

About postflop, against someone this wide you need to have an undefined calling range, wide enough to play back on more than broadway boards like you correctly noticed a problem. If you only call AQ, AJs, KQ, KJs it's too easy to play vs you. I would defend very wide here vs 15% 3bet that is likely >15% in these positions. Probably a snap call pre with 97s and better.. Now you can play back on just about any board.